4-Ethylaniline is primarily used as an intermediate in the synthesis of dyes and pigments, particularly in the production of azo dyes, which are widely employed in the textile, paper, and leather industries. Its ability to form stable diazonium salts makes it valuable for creating vibrant and durable colorants. Additionally, it is utilized in the manufacture of certain agrochemicals, including herbicides and pesticides, where it serves as a building block for active ingredients. In the pharmaceutical sector, 4-Ethylaniline is employed in the synthesis of specific organic compounds and active pharmaceutical ingredients (APIs). Its applications also extend to research and development, where it is used as a reagent in organic chemistry for studying reaction mechanisms and developing new chemical entities.